Field of the Disclosure
The present application relates to a display device, and more particularly to a display device adapted to enhance flexibility and touch sensitivity.
Description of the Related Art
Nowadays, a display field for visually representing an electrical information signal has been rapidly developed with the spread of information society. In accordance therewith, a variety of flat panel display devices with features, such as slimness, light weight and low power consumption have been developed. Also, the flat panel display devices have been rapidly replacing the existing cathode ray tubes (CRTs).
As examples of the flat panel display devices, liquid crystal display (LCD) devices, organic light emitting display (OLED) devices, electrophoretic display (electric paper display (EPD)) devices, plasma display panel (PDP) devices, field emission display (FED) devices, electroluminescence display devices (ELDs), elector-wetting display (EWD) devices, and so on can be introduced.
Also, as the display devices are actively developed, it requires that the display devices have diversity distinguished from the existing designs, enhance esthethic values, and provide useful multi-functions to use. In accordance therewith, a flexible display device using a flexible material such as a plastic material and so on is developed. The flexible display device can be designed in a variety of shapes, unlike the flat panel display device of the related art.
A cover substrate can be applied to a screen of the display device. The cover substrate can be used to protect the display device. As such, it is necessary for the cover substrate to secure high hardness and high impact resistance. Also, the cover substrate can be applied to a flexible display device. To this end, the cover substrate must secure flexibility.
As a cover substrate of the related art, a tempered glass is being mainly used. The tempered glass has poor molding characteristics. Due to this, it is difficult for the tempered glass to apply to the flexible display device.
To address this matter, a cover substrate formed from a plastic material with superior molding characteristics is being actively researched. However, the plastic material has a lower surface strength compared to a glass material. As such, the plastic cover substrate has a poor scratch-resistance characteristic and is easily deformed under high temperature and humidity circumstances. Due to this, the plastic cover substrate must deteriorate reliability of the display device.
Also, a touch panel is being applied to a display device. The touch panel can input data by touching an input device, such as a finger, a stylus or others, and images are displayed on the display device. Such a touch panel can be largely classified into an electrostatic capacity type and a resistant film type.
The resistant film type touch panel senses a variation of the resistance and detects a touch position. The electrostatic capacity type touch panel senses a variation of the capacitance between electrodes and detects a touch position when it is touched by a finger. The resistant film type touch panel can cause deterioration of performance and scratches by being repeatedly used. Due to this, the electrostatic capacity type touch panel with superior durability and long lifespan becomes the center of public interest.
In order to smoothly drive such a touch panel applied to the display device, a thick cover substrate is preferable to have a high dielectric constant. In most cases, the plastic materials have lower dielectric constants compared to the tempered glass materials. Due to this, a cover substrate formed from a plastic material must deteriorate touch sensitivity of the touch panel which is applied to the display device.
In view of these points, it is necessary to develop a cover substrate which has superior surface hardness and flexibility (or moldability) and maintains superior reliability under high temperature and humidity circumferences without deteriorating any touch sensitivity.